1.0 Field of the Invention
The present invention generally concerns irrigation control and controllers. The present invention more particularly concerns solid-state digital irrigation controllers that have keys and displays and that accept user parameterization, commonly called "programming", of complex irrigation sequences and modes of operation.
2.0 Background of the Invention
Irrigation control has progressed from simple timed actuation, i.e., of switches or valves, to programmed control. Examples of existing programmed control include computation of total irrigation watering duration based on zone description, type of sprinkler components controlled, soil type and broad plant type categories (e.g., lawn vs. shrub).
One problem with previous irrigation control is that it has not been possible to specify a time period in which no watering is to occur. For example, facilities used by people are not usually irrigated when people are not likely to be present. Although undesired irrigation can be avoided by manual setting of all watering periods, this is inefficient, inconvenient, and incompatible with automated extrapolation of periodic irrigation cycles from supplied information.
Another aspect of existing programmed control is the use of a water budget feature. The water budget feature permits increasing or decreasing the watering time by a variable percentage. In theory the feature saves water by allowing reduction in the increases in the watering durations by a fixed percentage when the weather is wetter and/or cooler than expected. Many sprinkler heads apply water faster than the soil can absorb it, especially for sites with heavy clay soil, and/or sites with slopes and mounds. If water runs off or puddles from a normal irrigation cycle duration then runoff is even more pronounced when the water budget is set to 150%. One approach has been to divide the watering duration into two (2) cycles any time that the budget factor exceeds 150%. This gross division does not deal with a variety of conditions at the irrigation site, e.g., a site that cannot accept a 49% increase in watering duration.
Another problem exists with keeping track of total irrigation watering times at each irrigation station. Some existing irrigation controllers require the start times be entered for each irrigation repeat cycle with each separate irrigation station operating sequentially from this time. This is because hydrostatic pressure limitations in some irrigation systems demand that no more than one station should be irrigating, i.e., only one valve should be open, at any one time. For example, for each of eight stations performing three twenty-minute irrigation cycles, if station 1 starts at 12:00 midnight then station 2 may start at 12:20 a.m. and so on until station 8 may be scheduled to start at 2:20 a.m. Then station 1 may start again at 2:40 a.m. The number of cycles to be set is dictated by the total irrigation time divided by the individual irrigation cycle duration. Manual selection of such irrigation schedules for each individual irrigation station is difficult since it is particularly easy to lose track of how much total watering time is being entered. This tends to lead to inaccuracies that undesirably result in overwatering or underwatering.
The complexities inherent in stagger-scheduling irrigation of a number of irrigation stations are compounded by reducing the durations of individual irrigation cycles. For example, in the previous example where eight stations must each irrigate for one hour total duration, programming convenience might suggest a schedule of twelve irrigation cycles of five minutes each for each station. Station 1 would irrigate for five minutes starting each hour on the hour from midnight to 11:00 p.m. during twelve total irrigation cycles of five minutes each. Station 2 would start five minutes past the hour during the hours from 12:05 a.m. to 11:05 p.m. With existing irrigation controllers and valves these repeated short cycles use more energy, and induce more wear, in the valves. More importantly, this easy programming of shorter cycles may not permit sufficient ground penetration of irrigation water in certain types of soils with certain types of sprinklers.
Another problem arises when irrigation cycles are programmed too closely to one another. For example, if two stations only are controlled to irrigate during ten minute cycles for six total cycles each, giving a total watering duration of one hour at each station, an irrigation schedule that alternates between the two stations every ten minutes commonly results. This short off time (10 minutes) between the irrigation cycles at each of the two stations often results in insufficient soak time at each station between successive cycles. Water run off and wastage may result.
Existing irrigation control on one schedule cannot simultaneously integrate another schedule, e.g., long and infrequent deep watering cycles or short and frequent syringe cycles. For example, existing irrigation control does not allow a "periodic deep watering cycle" to be scheduled. Such a cycle would allow periodic long watering cycles for deep watering trees planted in lawns, or for flushing out salts in drip applications. For example, a shallow-rooted bluegrass lawn planted at a site with loamy soil and irrigated with spray heads having a precipitation rate of 1.7 inches per hour might be scheduled to water every other day (3.5 times per week) during the warm season for 15 minutes total watering duration. This schedule would apply about 0.4 inches of water per watering day (or about 1.5 inches per week). This schedule might be fine for watering the lawns, but not for trees.
To deep water trees planted in lawns, every 45 days an additional 80 minute cycle would be appropriate. This would apply 2.3 inches of water in order to soak the soil to a depth of almost 3 feet. With existing irrigation equipment the only easy and effective way to deep water trees in lawns is to install separate valves and bubblers for the trees. This involves extra cost and is rarely done.
Existing irrigation control doesn't permit the performance of periodic syringe irrigation cycles (multiple short irrigation cycles) until the completion of the normal irrigation watering schedule. In a desert, it would be desirable to schedule syringes to occur, for example, at one hour intervals every day from 9:00 am to 6:00 pm during the hot months of June through September. These cooling syringes would be in addition to the regularly scheduled irrigation cycles. In cold climates, syringe cycles can be specified for "frost wipe" applications to prevent damage to frosted turf, such as when people walk during early morning on frost-covered golf courses.
In summary, the failure to provide excluded watering time intervals in periodic (cyclic) irrigation control/controllers; to overcome deficiencies in water budgeting; to control total watering duration to eliminate underwatering or overwatering; to eliminate insufficient station on times; to avoid insufficient station off times; and to provide periodic alternate watering schedules such as periodic deep watering cycles or frequent syringe cycles are typical deficiencies of existing irrigation control. Improvements in these areas would, be expected to save money on water while reducing problems with plant disease, runoff, slope and pavement erosion, and liability for damages associated with underwatering and overwatering.